How do I fix this problem under BIND 9 named server? This error means you set wrong zone serial number. You must increment zone serial number. But, if you decremented the zone serial number you will get this error. In this example, zone serial number is set to 2008090816:

When you made changes to zone file increase zone serial number by one i.e. change 2008090816 to 2008090817 (but not to 2008090815). Save and close the file. Finally, reload named as follows:rndc reload && tail -f /var/log/messages